MIMOSELLA GRACILIS. 



557 



regularly branched, which rise from a mass of ramified 

 and interlacing tubes ; the branches opposite, either 

 short and simple pinnse, or elongate tapering shoots 

 pinnate or bipinnatc, the pinnse divided by joints into 

 veiy short internodes, each of which supports a pair of 

 cells. Zooecia ovate, biserial, opposite, borne chiefly on 

 the pinnffi and rarely on the principal stems, folded 

 together when the polypides are retracted, but thrown 

 back and standing out from the side of the pinna when 

 they expand. 

 Polypide with 8 tentacles. 



This beautiful species is a very free grower, and forms 

 large intricate masses, which hang in festoons about the 

 stems of the Halidrys, on which it is always found. The 

 ramification is irregular and luxuriant ; the tall flexile 

 stems, which are much attenuated towards the extre- 

 mity and run out into filamentary, tendril-like prolonga- 

 tions, are thickly set, now with short pinnae, now with 

 long, slender, tapering branches 

 either pinnate or bi- and tripinnate. 

 Not unfreqnently these are replaced 

 by longer shoots, much and variously 

 branched, which are copies of the 

 principal stems. The pinnse or 

 branches originate immediately be- 

 low a joint and tend upwards, so 

 as to form with the stem an acute 

 angle; the pairs very frequently 

 spring from different aspects of the 

 shoot. 



Towards the base of the pinnae the 

 zooecia are tall and oval ; as they 

 approach the apex they become short 

 and globose, and at last are nothing Upper portion of pinna. 

 more than little round excrescences. 



Fig. 34. 



